Sandwich structural composite panels are widely used in structures due to their low weight and their high strength. This is particularly true in structures that require high-strength to endure the environment in which the structure is to be used, and low weight for fuel efficiency, for example in aircraft.
The typical construction of a sandwich structural composite panel is comprised of a core panel with a front face sheet and a rear face sheet on opposite sides of the core panel. A layer of adhesive secures the front face sheet to one side of the core panel and a layer of adhesive secures the rear face sheet to the opposite side of the core panel.
The core panel between the front face sheet and the rear face sheet of a sandwich structural composite is often comprised of a plurality of open cells, for example honeycomb open cells. The plurality of open cells adds strength to the sandwich structural composite without significantly increasing weight. However, the presence of the open cells in the interior of the structural composite panel presents a problem when it is desirable to secure a threaded fastener to the structural composite. There is nothing inside the open cells for a threaded fastener to secure to.
Inserts have been developed that are used to secure a threaded fastener in a sandwich structural composite panel. Basically, a hole is formed in the sandwich structural composite panel and the insert is then inserted into the hole. The threaded fastener is then screw threaded into the insert in securing the fastener to the composite panel. However, the use of the fastener inserts adds weight to the composite panel. For every fastener it is desired to secured to the composite panel, a fastener insert is required. The need for the insert substantially doubles the weight of the each threaded fastener secured to the composite panel.